The British government Thursday rejected the ruling of a U.N. panel, which has reportedly decided that WikiLeaks founder Julian Assange has been illegally detained in the Ecuadorian embassy in London for over three years.

It added that the U.K. had a legal obligation to extradite Assange to Sweden, as he was the subject of an outstanding European arrest warrant.

Assange has been sheltering in the embassy since June 2012, after he was charged with sex crimes in Sweden. He was granted asylum in Ecuador but was unable to leave the U.K. without being arrested and facing extradition proceedings to Sweden.

The WikiLeaks founder denies the allegations against him and has maintained that they are politically motivated. He has also expressed fears that, if sent to Sweden, he could face extradition to the U.S., where he could face charges for the website's disclosure of classified U.S. information.

Anna Ekberg, spokesperson for the Swedish Foreign Ministry, told The Guardian: “The U.N. working group on arbitrary detention has concluded that Mr. Assange is arbitrarily detained. The working group’s view differs from that of the Swedish authorities. We will forward a reply to the working group tomorrow. It will be more clear tomorrow why we reject the working group’s conclusions.”

The U.N. panel's official ruling on Assange's detention is scheduled to be published on Friday.